The role of cysteine in the regulation of blood glutathione-protein mixed disulfides in rats treated with diamide.
The kinetics of GSH, GSSG, and thiol-protein mixed disulfides (RS-SP) of GSH (GS-SP) and cysteine (CYS-SP) were studied in rat blood and liver in the time range 0-120 min after treatment with 100 and 200 mg/kg i.p. of diamide. Total consumption (10 min) and regeneration (120 min) of blood GSH, matched by parallel increases and decreases in RS-SP, were observed. GSSG did not change appreciably. No dose-effect relationship was obtained with either treatment. On the contrary, in vitro treatment of blood with 0.75 mM diamide provoked the same trends of GSH and RS-SP as in vivo (e.g., reversible modifications), whereas treatment with 1.5 mM caused drops and rises in GSH and RS-SP, respectively, without any subsequent return to control values. The presence of a hematic factor responsible for RS-SP regulation is hypothesized in the in vivo experiment. Successive experiments involving in vitro pretreatment with 2 mM diamide and treatment with 0.5 mM of various thiols indicated that cysteine (CYS), but not GSH or N-acetylcysteine, rapidly restored erythrocyte GSH and RS-SP to their basal levels. No evident sign of hemolysis was observed in these experiments. These results indicate that CYS is a diffusible thiol important for RS-SP regulation. Analysis of whole blood of rats treated with 100 mg/kg i.p. diamide and the presence of two reversible peaks (about 10 times the corresponding control level) of CYS-SP and free CYS confirmed the plausible role of CYS in maintaining the reversibility of the process. Preliminary results in liver of rats treated with 100 mg/kg diamide indicated that CYS may act by metabolic cooperation between organs. We suggest that CYS may have a role in the regulation of the intracellular redox state of rat erythrocytes during oxidative stress.
Di Simplicio
P
P
Department of Environmental Biology, University of Siena, Italy.
Giannerini
F
F
Giustarini
D
D
Lusini
L
L
Rossi
R
R
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000502:physiology*; D003958:Diamide / Q000494:pharmacology*; D004220:Disulfides / Q000097:blood*; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D005978:Glutathione / Q000097:blood*; D019803:Glutathione Disulfide / Q000097:blood*; D066298:In Vitro Techniques; D007274:Injections, Intraperitoneal; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013439:Sulfhydryl Reagents / Q000494:pharmacology*
D004220:Disulfides; D013439:Sulfhydryl Reagents; D003958:Diamide; D005978:Glutathione; D003545:Cysteine; D019803:Glutathione Disulfide